1. Field of Invention
The present invention relates generally optical systems and apparatus, in particular, to optical lenses having extended depth of field.
2. Discussion of Related Art
Several approaches have been developed for obtaining extended depth of field of an optical apparatus. Recent technologies involving extended depth of field for various optical applications, including ophthalmic applications, are using annular grooves across a standard lens to create a phase retardation that leads to an interference pattern along the focal distance which, when controlled properly, can provide an extended depth of field. An example of this approach is described in U.S. Pat. No. 7,365,917, which is incorporated herein by reference in its entirety. Other techniques for extending the depth of field include presenting diffractional optic elements that can diffract the optical signal into different diffraction orders thereby realizing a bi-focal or multi-focal lens that allows a clear vision for different object distances using a single passive lens. Both technologies implement phase reshaping by introducing a lateral (i.e., along the surface of the lens) geometrical lens reshaping that produces the required phase retardation along a few microns in the longitudinal axis of the lens.